SOT Temperature Sensor with Multidrop Single-Wire Digital Interface

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1 General Description The MAX6575L/H is a low-cost, low-current temperature sensor with a single-wire digital interface. It features accuracy of ±3 C at +25 C, ±4.5 C at +85 C, and ±5 C at +125 C. The MAX6575L/H is a monostable, externally triggered temperature sensor that allows a microproces sor (μp) to interface with up to eight temperature sensors using a single control line. Temperatures are sensed by measuring the time delay between the falling edge of the external triggering pulse and the falling edge of the subsequent pulse delays reported from the devices. Different sensors on the same I/O line use different timeout multipliers to avoid overlapping signals. The MAX6575L/H features eight different timeout multipliers; these are selectable by using the two time-select pins on each device and choosing the L or H version. The L version provides four delay ranges less than 50ms. The H version provides four delay ranges greater than 50ms. The MAX6575L/H is available in a space-saving 6-pin SOT23 package. Applications Critical μp and μc Temperature Monitoring Portable Battery-Powered Equipment Cell Phones Battery Packs Hard Drives/Tape Drives Networking and Telecom Equipment Medical Equipment Typical Operating Circuit Features Simple Single-Wire Interface to μp or μc Multidrop up to Eight Sensors on One Wire ±0.8 C Accuracy at +25 C (±3 C max) Operates from +2.7V to +5.5V Supply Voltage Low 150μA (typ) Supply Current Standard Operating Temperature Range -40 C to +125 C Small 6-Pin SOT23 Package Ordering Information PART TEMP.RANGE PIN- PACKAGE Pin Configuration appears at end of data sheet. SOT TOP MARK MAX6575LZUT -40 C to +125 C 6 SOT23 AABG MAX6575HZUT -40 C to +125 C 6 SOT23 AABH Selector Guide PART TIMEOUT MULTIPLIERS (µs/ K) MAX6575L 5, 20, 40, 80 MAX6575H 160, 320, 480, V TO +5.5V VCC 0.1µF VDD 0.1µF VDD 0.1µF MAX6575L MAX6575H VCC 10kΩ TS1 TS0 TS1 CHIP #1 CHIP #8 TS0 I/O I/O µp I/O ; Rev 1; 11/14

2 Absolute Maximum Ratings Terminal Voltage (with respect to ) V DD V to +6V TS1, TS V to (V DD + 0.3V) I/O V to +6V Input/Output Current, All Pins...±20mA Continuous Power Dissipation (T A = +70 C) 6-Pin SOT23 (derate 7.10mW/ C above +70 C)...571mW Operating Temperature Range C to +125 C Storage Temperature Range C to +150 C Lead Temperature (soldering, 10s) C Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Electrical Characteristics (V DD = +2.7V to +5.5V, T A = -40 C to +125 C, unless otherwise noted. Typical values are specified at T A = +25 C and V DD = +5V, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS V DD Range V DD V Supply Current I DD V DD = 5.5V Temperature Sensor Error (Note 1) Output Pulse Delay Note 1: See Temperature Accuracy histograms in Typical Operating Characteristics. Note 2: Guaranteed by design. Not production tested. Note 3: Limit maximum start pulse at 1ms to avoid timing overlap. Note 4: If no reset pulse is applied. T A = -40 C to +85 C T A = -40 C to +125 C 400 T A = -20 C -7.5 ± T A = 0 C -5.5 ± T A = +25 C -3.0 ± T A = +85 C -4.5 ± T A = +125 C -5.0 ± t D1 V TS1 =, V TS0 = 5T t MAX6575L, D2 V TS1 =, V TS0 = V DD 20T T (temp) in K, t D3 Figure 1 V TS1 = V DD, V TS0 = 40T t D4 V TS1 = V DD, V TS0 = V DD 80T t D5 V TS1 =, V TS0 = 160T t MAX6575H, D6 V TS1 =, V TS0 = V DD 320T T (temp) in K, t D7 Figure 1 V TS1 = V DD, V TS0 = 480T t D8 V TS1 = V DD, V TS0 = V DD 640T Output Pulse Low Time t L1-8 Figure 1 5T µs Reset Pulse Width (Note 2) t RESET Figure ms Setup Time t SETUP Figure 1 10 µs Start Pulse (Note 3) t START Figure 1, T A = +25 C 2.5 µs Delay Time from Trigger to Ready (Note 4) t READY Figure ms Glitch Immunity on I/O Input 500 ns Time-Select Pin Logic Levels V IL 0.8 V IH 2.3 V I/O Output Voltage Low V DD > 4.5V, I SINK = 3.2mA 0.4 OL V DD > 2.7V, I SINK = 1.2mA 0.3 I/O Input Voltage Low V IL 0.8 V I/O Input Voltage High V IH 2.3 V µa C µs V V Maxim Integrated 2

3 Typical Operating Characteristics (V DD = +5V, T A = +25 C, unless otherwise noted.) PERCENTAGE OF PARTS SAMPLED (%) TEMPERATURE ACCURACY (T A = +25 C) SAMPLE SIZE = ACCURACY ( C) MAX6575 toc01 PERCENTAGE OF PARTS SAMPLED (%) TEMPERATURE ACCURACY (T A = +85 C) SAMPLE SIZE = ACCURACY ( C) MAX6575 toc02 ACCURACY ( C) ACCURACY vs. TEMPERATURE TEMPERATURE ( C) MAX6576 toc3a SUPPLY CURRENT (µa) SUPPLY CURRENT vs. TEMPERATURE MAX6575 toc03b +15 C/div THERMAL STEP RESPONSE IN PERFLUORINATED FLUID MAX6575 toc04 MOUNTED ON 0.75 in.2 OF 2oz. COPPER C C/div THERMAL STEP RESPONSE IN STILL AIR MAX6575 toc05 MOUNTED ON 0.75 in.2 OF 2oz. COPPER +100 C +25 C TEMPERATURE ( C) 5sec/div 20sec/div Pin Configuration PIN NAME FUNCTION 1 V DD Positive Supply Voltage 2 Ground 3 N.C. No Connect. Connect pin to or leave open. 4, 5 TS0, TS1 Time-Select Pins. Set the time delay factor by connecting TS1 and TS0 to either V DD or. See Table 1. 6 I/O Bidirectional Interface Pin. A time delay between when the part is initiated externally by pulling I/O low and when the part subsequently pulls I/O low, is proportional to absolute temperature ( K). Maxim Integrated 3

4 Detailed Description The MAX6575L/H low-cost, low-current (150μA typ) temperature sensor is ideal for interfacing with microcon trollers or microprocessors. The MAX6575L/H is a monostable, externally triggered temperature sensor that uses a Temp Delay conversion to communicate with a μp over a single I/O line. Time-select pins (TS1, TS0) permit the internal temperature-controlled oscillator (TCO) to be scaled by four preset timeout multipliers, allowing eight separate temperature sensors to share one I/O line. Different sensors on the same I/O line will use different timeout multipliers to avoid overlapping signals. Operating the MAX6575L/H Figure 1 illustrates the timing for the MAX6575L/H. When the device is powered up, it assumes a ready state where it awaits an external trigger at the I/O pin. The I/O pin of the MAX6575L/H has an open-drain output structure that requires a pullup resistor to maintain the proper logic levels. Once the I/O pin is pulled low and then released, control of the I/O pin is transferred to the MAX6575L/H. The temperature conversion begins on the falling edge of the externally triggered pulse. The I/O line is pulled low at a later time. That time is determined by the device temperature and the Time Select pins (TS1, TS0). The I/O line remains low for 5Tμs, where T is the temperature in degrees Kelvin. The temperature of the device is represented by the edgeto-edge delay of the externally triggered pulse and the falling edge of the subsequent pulse originating from the device. The device can be manually reset by pulling the I/O line low for more than t RESET (16ms max). The device will automatically reset after a Table 1. Time-Select Pin Configuration maximum delay of 520ms, at which point it will again be in a ready state awaiting a start pulse. Definition of Terms: t RESET : Time I/O must be externally pulled low to guarantee the MAX6575L/H is in a ready state awaiting external trigger. (Part will assume a ready state after 520ms without a reset pulse.) t SETUP : Time I/O must be high prior to a start pulse. t START : Trigger pulse which starts the on-chip timing sequence on its falling edge. t Dx : TIME-SELECT PINS TIMEOUT MULTIPLIERS (μs/ K) TS1 TS0 MAX6575L MAX6575H VDD VDD VDD VDD Timing delay between the falling edge of the start pulse and the falling edge initiated by CHIP#x. t Lx: I/O pulse low time (5Tμs). t READY : Time after falling edge of start pulse when the MAX6575L/H will reset itself and await the next external trigger. The temperature, in degrees Celsius, may be calculated as follows: T( C) = [t Dx(μs) / timeout multiplier(μs/ K)] K t SETUP APPLIED START PULSE CHIP# 1 RESPONSE CHIP# 2 RESPONSE CHIP# 3 RESPONSE CHIP# 4 RESPONSE t RESET t START t L1 tl2 D1 t D2 t L3 t L4 t D3 t D4 t READY Figure 1. Timing Diagram Maxim Integrated 4

5 Table 2. Allowable Temperature Differential ( C) TIMEOUT MULTIPLIER MAX6575L Table 3. Typical Peak Noise Amplitude MAX6575H >165 >165 >165 >165 >165 >165 > >165 >165 >165 >165 > >165 >165 >165 > >165 >165 > >165 >165 > > PARAMETER MAX6575L MAX6575H Timeout Multiplier Noise Amplitude ( C) ±0.33 ±0.15 ±0.15 ±0.098 ±0.091 ±0.063 ±0.043 ±0.037 Time-Select Pins (TS1, TS0) Table 1 shows the configuration of the Time-select pins for the MAX6575L/H. Each device allows four selectable timeout multipliers intended to prevent overlapping when multiple devices are used on the same I/O line. Tie TS1 and TS0 to either or V DD to select the desired temperature multiplier. To monitor several chips on the same I/O line, different timeout multipliers should be selected using the TS1 and TS0 pins. The timeout periods are then scaled so that the response times will not overlap (see Timeout Selection). Applications Information Timeout Selection Under extreme temperature conditions, it is possible for an overlap to occur between the timeout delays of different sensors in a multidrop configuration. This overlap can occur only if the temperature differential recorded between two devices is very large. Timeout overlaps can be avoided in multidrop configurations by selecting the appropriate timeout multipliers. Table 2 illustrates the allowable temperature differential between devices when the maximum error is present on each device. Allowable temperature differentials greater than 165 C indicate no overlap. For example, if the maximum temperature differential in a system is 80 C, the only combinations of timeout multipliers that could result in timeout overlap would be a 320:480μs/ K (70.2 C) or a 480:640μs/ K (37.9 C) combination. As long as these combinations of timeout multipliers are not used in the same multidrop configuration, no overlap can occur. Thus, seven MAX6575L/H parts can be used in the same multidrop configuration if the maximum temperature differential between parts is 80 C. A similar analysis shows that four MAX6575L/H parts can be used when the maximum temperature differential extends over the entire 165 C range of the part. Noise Considerations The accuracy of the MAX6575L/H timeout delay is susceptible to noise generated both internally and externally. The effects of external noise can be minimized by placing a 0.1μF ceramic bypass capacitor close to the device s supply pin. Internal noise is inherent in the operation of the device and is detailed in Table 3. Internal averaging minimizes the effect of this noise when using longer timeout multipliers. The effects of this noise are included in the overall accuracy of the device as specified in the Electrical Characteristics table. Maxim Integrated 5

6 +2.7V TO +5.5V +2.7V TO +5.5V V DD 0.1µF V DD 0.1µF MAX6575L MAX6575L 40µs/ K TS1 TS0 I/O T1 80µs/ K TS1 TS0 I/O T2 V CC 470Ω (8) 10kΩ P P1.0 P1.1 P1.2 P1.3 V CC P1.4 P1.5 OPEN: T1 CLOSED: T2 10kΩ P3.5 P1.6 P1.7 22pF X1 12MHz X2 22pF Figure 2. Interfacing Multiple Devices with a Microcontroller Interfacing Multiple Devices with a Microcontroller Figure 2 shows how to interface multiple MAX6575L/H devices with an 8051 microcontroller. The first device, T1, is configured for a timeout multiplier of 40μs/ K, while the second device, T2, is configured for a timeout multiplier of 80μs/ K to avoid overlap. The microcontroller takes in temperature values from both sensors, T1 and T2, on a single port pin, P3.7. The microcontroller displays five times the temperature in degrees Celsius in binary on Port 1. A switch connected to a pull-up resistor at Port 3.5 selects which temperature is displayed: open = T1, closed = T2. Code is provided for this application as Listing 1. Maxim Integrated 6

7 Listing Code Example Maxim Integrated 7

8 Listing Code Example (continued) Maxim Integrated 8

9 Listing Code Example (continued) Pin Configuration TOP VIEW V DD N.C. 1 4 I/O 2 3 MAX6575L MAX6575H SOT TS1 TS0 Package Information For the latest package outline information and land patterns (footprints), go to Note that a +, #, or - in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 6 SOT23 U Maxim Integrated 9

10 Revision History REVISION NUMBER REVISION DATE DESCRIPTION PAGES CHANGED 0 4/99 Initial release 1 11/14 Removed automotive reference from data sheet 1 For pricing, delivery, and ordering information, please contact Maxim Direct at , or visit Maxim Integrated s website at Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance. Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc Maxim Integrated Products, Inc. 10